Highest Temperatures Ever Recorded in Every Midwestern State

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A heatwave that began in the Southeastern United States is making its way north, through parts of the Midwest this week. A heat dome stretching up through the Mississippi and Ohio River Valleys is forecast to bring triple-digit, potentially record-breaking temperatures, to several Midwestern cities – from St. Louis and Kansas City, to those as far north as Chicago and Minneapolis.

While the Midwest is generally not as hot as the Southern United States in the summer months, the region’s heavy reliance on agriculture – particularly corn production – is expected to exacerbate the heat wave’s impact. Several Midwestern states have long been among the largest corn producers in the United States. When temperatures rise, corn crops release moisture into the atmosphere, colloquially known as “corn sweat,” at a rate of 3,000 to 4,000 gallons per acre, per day, according to the U.S. Geological Survey. In these conditions, corn crops in Iowa alone release as much as 56 billion gallons of water into the atmosphere every day, driving up humidity.

High levels of humidity can make hot days feel even hotter, and increase the risk of certain heat-related maladies, including dehydration, muscle cramps, heat stroke, and heat exhaustion. Even if the mercury does not hit all-time highs in the Midwest this week, the added effects of humidity may make the heat feel record-breaking in many parts of the region.

Using data from the National Oceanic and Atmospheric Administration’s State Climate Extremes Committee, Climate Crisis 247 identified the hottest temperatures ever recorded in each state in the Midwest. Supplemental date and location data for each state’s record-high temperature are also from NOAA. Midwestern states were determined using the classification system established by the U.S. Census Bureau. States are listed in alphabetical order.

Across the 12 states on this list, record high temperatures range from 112°F to 121°F. In each of these states, all-time high temperatures were reported in the month of July.

Illinois

Highest temperature on record: 117°F
Most recent date of record-high: July 14, 1954
Location of weather station(s) that reported record heat: East St. Louis

Indiana

Highest temperature on record: 116°F
Most recent date of record-high: July 14, 1936
Location of weather station(s) that reported record heat: Collegeville (South of Rensselaer)